In hydropneumatic devices such as diaphragm accumulators or piston accumulators, the prior art involves filling processes or checking processes in which the gas filling pressure is monitored. On the filling or checking port, a closure screw is tightened to block the port gastight and is loosened forming a flow path with a passage size sufficient for the filling or checking process. The execution of these processes is relatively simple if, before loosening the closure screw, a filling and checking device is attached to the port of the tank. In the event that such device attached tightly to the port is not used, a not inconsiderable hazard potential exists if it is improperly operated, i.e., not according to specifications. According to specifications, the procedure should include loosening the closure screw, for example, by a manually activated hexagon socket wrench, simply by a small amount, for example, on the order of one half turn. If this specification is not met, and the screw is not only loosened, but turned too far, the danger exists that the closure screw will be ejected by force by the gas pressure which has not yet decreased. If a filling and checking device is not attached to the port, the device will also be ejected from the tank by force. These ejections endanger the vicinity and constitute a corresponding accident hazard for personnel. This danger prevails mainly when, instead of a manual turning tool, a power tool is used, such as, for example, a power drill.